Balancing crankshafts



BALANCING CRANKSHAFTS- Filed May 21, 1923 5 Sheets-Sheet 1 -INVENTOR.

A TTORNEY.

Dec. 14, 1926.

1,610,718 c. P. THOMAS BALANC I NG GRANKSHAFTS Filed May 21, 1923 3Sheets-Sheet 5 INVENTOR.

ATTORNEY.

Patented Dec. 14, 1926.

UNITED STATES cnngtns r; THOMAS, or LANSING, MICHIGAN.

BALANCING CRANKSHAFTS.

Application filed. May 21,

My invention relates to balancing crankshafts for engines and includes aprocess preliminary to placing the same in a conventional balancingmachine.

In the balancing of crankshafts as now practiced the shaft is put into aconventional machine for the purpose and set in rapid rotation and themachine is adjusted first to indicate the static balance of the shafts.The shaft is then taken out and corrected as indicated. It is thenplaced back readjusted in the machine and again whirled and indicatedfor the'dynamic balance and is then taken out and corrected for thisindication.

My invention relates to an apparatus and process of treating the shaftbefore putting it into the conventional balancing'machine so that timeis saved and accuracy secured.

In the accompanying drawings;-

Figure 1' is a plan View of an apparatus for performing the process ofmy invention with a six-cylinder crankshaft in place thereon.

Fig. 2 is a section on the line IIl[I, Fig. 1, looking in the directionof the arrows.

Fig, 8 is a detail end elevation looking from the left of Fig. 1 showinga shaft raised from the knife edge.

Fig. 4 is a section on the line IVIV, Fig. 3, looking in the directionof the arrow.

Fig. 5 is a view similar to Fig. 8 showing the crankshaft resting uponthe knife edge and free .to roll slightly thereon.

Fig. 6 is a section on the line VIVI, Fig. 1. i

Fig. 7 is an end elevation looking-from the right of Fig. 6 Y

a is the base of the supporting frame for the shaft. (6 is a lateralprojection from the same at the center thereof as shown in Fig. 1 butcapable of sliding along said base while maintaining its relativeposition extending at approximately right angles to said base a a arevertical standards rising up from the ends of the base a. 7), Z) arelong knife-edge supports which are secured, by friction or otherwise, intransverse grooves in the tops of the standards a a a is a rockshaftextending parallel to the edge of the base a and above the same, itsends extending through hearings in the standards a a is a lever arm orhandle by which theshaft 0 may be rocked. c is radiallyextending armsecured on the end of 'the shaft The mechanism at one 1923. Serial No.640,393.

end of the frame is the same as that at the other so that onedescription will apply to both mechanisms. an arm 0 on each end of therockshaft 0, d is a plate pivoted at having at its center a cut-awayportion 6Z3 adapted to receive the end arbor of the shaft. 0 is an armof a toggle joint, one end of which is pivoted to the free end of theplate cl and the other to the free end of the arm 0 When the handle 0 isdepressed, as shown in Fig. 3, the plate 03 at each end of thesupporting frame is raised, as shown in Fig. 3, and the shaft issupported above and away from the knife edge Z). When the handle 0 israised the plate (l is lowered and the shaft is There is, for instance,

allowed to rest at each end upon the knife edges 5, b, as shown in Fig.5', in a known and predetermined position.

e is a broad-based standard adapted to be set and remain at anydesiredposition in a wide groove in the lateral extension at from thebase a. e is a scale arm pivoted on. a knife-edge toward its center tothe upper end of the standard c. There is a graduation as shown alongone arm of the lever 6 e is a poise or weight adapted to be adjusted tovarious positions along the scale upon the lever arm a e is a longdepending counterweight by which the scale lever e is balanced about itspivot in the upper end of the standard 6. e is a standard at the outerends of the lateral projection 4 The end of the scale beam or lever 6passes into a slot in the standard 6 and is limited in its movement bythe ends of said slot or by a transverse rod passing through saidstandard or otherwise. 6 is a knife-edge pin extending laterally fromthe scale arm or lever 6' upon the opposite side of its pivot in thestandard 6 from that at which the poise c is located. 6 is a saddleresting upon the knife-edge 6 The standards 6 and c are adjustable as toheight, as shown in Fig. 7. j

g g g are the arbors of a crankshaft which rest in hearings on theengine when adjusted to postion therein. 7L, it are parallel cranksadjacent to the ends of the crankshaft G. ]L2 h are parallel crankslocated symmetrically upon the crankshaft G next to the cranks h, h andat 120 degrees to the last-named cranks. a are coaxial cranks atthecenter of the shaft G. The crank pins of the cranks h 71? join eachother end to endso that only the outer radial arms are required. Thecranks 71,3, 71. are at an angle of 120 degrees to the arms 72?, 71. andh, h and are so constructed that (before balancing) they shall have asomewhat greater gravitational turning moment about the axis of theshaft than either of the pair of cranks h, h, or if, if.

The position of the standard 6 is so adjusted that the saddle 0 shallcome into posi tion to be engaged by a crank pin of one of the cranks71/ 7L3 when the crankshaft is placed in position on the frame of the machine, with another pair of cranks as 7L2,

vertically below said axis.

The adjustment of the apparatus anr. manner of performing the process isas follows:

The handle 0 is pressed downward, raising the plates (Z, (Z to theposition indicated in Fig. 3. The crankshaft is then placed in positionwith the arbors g, g resting in the notches or cavities a of the plates(Z, d and the shaft is turned about its axis until one of the cranksits, 72. rests on the saddle e. The handle 0 is then raised, the crankA3 being held firmly on the saddle at the same time by pressure of thehand. This lowers the blocks (Z, (Z, gently and permits the shaftbearings g, g to rest upon the knife edges Z), 6 and in this'positionthe cranks 7?, 7L3 and 7t, 71 are opposite each other and in the samehorizontal plane, the center line of each being 30 degrees above thehorizontal. A crank pin of a crank 72. [L3 then rests upon the saddle eand because 'of the greater weight of the cranks 71, h

with reference to the cranks 7r, h the saddle is pressed downward.raising the outer end of the scale arm. The poise e is then moved alongthe scale until the cranks h [L3 are raised and occupy the same angularposition upon one side of the center line of the crankshafts as thecranks h, it occupy upon the other side. The scale upon the scale arm issuch that it indicates the distanee that a certain sized drill will haveto be forced in axially to the crank pins of the crank 7b3 72.3 toremove the excess of weight of the cranks 172/3 over those of the crankh. The crankshaft is then taken out of the frame and the drill is forcedin, deepening the aperture indicated at h a, Fig. 2, which operationmakes the gravitational turning moment of the pair of cranks 72. 72,equal to that of the cranks it, 72. and leaves that of ]L2, 7L2 equallygreater than that of either of the other pairs h 71 and h, h. The shaftis then placed in the conventional balancing machine and whirled toindicate amount of static unbalance which amount is to be removed fromcranks kg, 71, and in an advantageous position to allow removal of aminimum amount of material at a maximum radial distance from the centerof the shaft.

The amount of dynamic unbalance is indicated in the usual way by placingthe shaft in the usual way in the conventional balancing machine.

The above mentioned explanation applies when the pair of cranks 7L2, 7L2have a greater gravitational turning moment than the pair 71., It. Ifthe opposite is the case it becomes necessary to make the gravitationalturning moment of the pair of cranks 72?, its equal to that of if, ifinstead of h, 72.. This necessitates weighing the moment of 72., II.when turned to a position which is 120 degrees from that in the firstmentioned case. This can, of course, be done by turning the heavy shaftend for end, which would bring the cranks it, 70" on the opposite sideof a vertical plane through the crank axis from the scale saddle andwould require rotation 130 degrees over said axis to get into the scale.I prefer, however, to slide the broadbased standard 6 under thecrankshaft until it brings the saddle e in position to receive a pin ofcrank 72 when rotated over the axis as described. To permit this, thebroad base 0 fits under gibs which hold it firmly but permit it to slidefreely. In a slot a in this base are flared stops 6 (2 with screwadjustment and clamping bolts 6 to fix their positions. Once adjustedthese two stops limit the movement of the base a one in one direction,the other in the other direction, so the saddle e is properly positionedunder the crank ha in either of the two hereinbefore describedpositions.

To avoid dirt and chips getting against the sliding surfaces the undersurface of the broad base of c is cut away, which prevents its motionbeing impeded by small obstacles. For use with cranks of shorter throwthe stops can be adjusted closer together and the height of thestandards 6 and a adjusted lower. A reverse adjustment will fit thedevice for cranks of longer throw.

The advantages of my invention become more apparent when it isremembered that the conventional whirling machine indicate; the angulardirection from the shaft axis of the excess weigl'it but does notindicate accurately the amount to be taken off each of the adjacentcranks when this direction falls between, as it commonly does. It is,therefore, necessary to correct more or less by guess and test againwith further guessing at each correction. the weight of one pair ofcranks is eliminated by hanging them directly below the crankshaft axis,and by weighing the difference between the other two and removing thisdifference by drilling along the of the heavy one with a known sizedrill for the distance indicated by the scale (the hole being startedbefore weighing), I balance the two pairs and need only remove metalfrom one pair after the whirling balance lVith my invention,

it to different crank shafts.

What I claim is:

1. The method of preparing a crankshaft having end cranks, center cranksand intermediate cranks, consisting in making the center cranks of agreater turning movement due to their weights than the end cranks,placing said crankshaft in a horizontal position so that it may rotate,arranging the end cranks and the center cranks at equal angularpositions to the horizontal and on opposite sides of the vertical planethrough the axis of the crankshaft with the inter mediate cranksvertical, measuring a preponderance of rotating effect of the centercranks, and removing material therefrom to remove said excess of turningmoment.

2. In an apparatus of the kind described, two standards provided withbearings for a multiple crankshaft, a scale beam adjacent to saidstandards, said scale beam being so located with reference to saidbearings that one of the cranks of said shaft shall engage upon saidscale beam at its proper angle, for the purpose described, said bearingsconsisting of prepared knife-edges as shown and described, plates havingnotches in their upper edges located adjacent to each of saidknifeedges, means for raising said plates up so as to receive the arborsof said crankshaft before they engage said knife-edges, and means forlowering said plates to allow said arbors to rest on said knife-edges.

3. In an apparatus of the kind described, the combination of twostandards provided with bearings adapted to receive amultiplecrank-shaft and permit it to rotate freely, and a scale beamlocated in position to have one of the cranks engage thereon at itsproper position for the purpose described, said scale beam beingadjustable to different sides of the vertical plane through the axis ofthecrank shaft.

4. The method of preparing a crankshaft having end cranks, center cranksand intermediate cranks, for a balancing machine, consisting in makingthe pairs of parallel cranks of different turning moments due to theirweights with the center cranks having the greater turning moment,placing said crankshaft in a horizontal position so that it may rotate,arranging the pair of cranks having the least gravitational turningmoment and the center cranks at equal angular positions to thehorizontal and on opposite sides of the vertical plane through the axisof the crankshaft with the other pair of cranks vertical, measuring apreponderance of rotating effect of the center cranks and removingmaterial therefrom to remove said excess of turning moment.

5. The method of preparing a crankshaft having end cranks, center cranksand intermediate cranks, for balancing in a balancing machine,consisting in making the center cranks of a greater turning moment dueto its Weight than the intermediate cranks and the intermediate cranksof greater turning 'moment due to their weight than the end cranks,placing said crankshaft in a horizontal position so that it may rotate,arranging the end cranks and the center cranks at equal angularpositions to the horizontal and on opposite sides to the vertical planeof the axis of the crankshaft with the inter mediate cranks vertical,measuring a preponderance of rotating effect of the center cranks andremoving material therefrom to remove said excess of turning moment.

6. In an apparatus of the kind described, the combination of twostandards provided with bearings adapted to receive amultiplecrank-shaft and permit it to rotate freely, and a scale beamlocated in position to have one ofthe cranks engage thereon at itsproper position for the purpose described, said scale beam beingprovided with a scale thereon graduated to indicate the amount of metalto be removed for the purpose described.

In testimony whereof, I sign this specification.

CHARLES P. THOMAS

